Stem cell niches are anatomical locations in tissues, where stem cells self-renew and generate differentiated progeny. Although a number of studies have focused on how niches maintain stem cell fate during tissue homeostasis, not much is known about their roles in establishing stem cells. The adult Drosophila midgut is maintained by intestinal stem cells (ISCs). Our recent findings have shed light on the mechanism by which these ISCs are specified during development. We have shown that a stem cell progenitor, also known as an (AMP) generates a niche cell through asymmetric Notch signaling. This niche, called a peripheral cell (PC) uses the BMP 2/4 homolog, decapentaplegic (dpp), to allow AMPs to divide in an undifferentiated state, and subsequently breaks down and dies, resulting in the specification of ISCs in the adult midgut. These studies demonstrate a new paradigm for stem cell-niche biology, where progenitors generate transient niches that determine stem cell fate, and could provide insights into how stem cells are established in other tissue. We will expand on our recent findings by addressing the following specific aims: 1. Investigate the mechanism by which ISCs are established and maintained during development. 2. Determine the roles of Notch, dpp and Jak-Stat signaling pathways in regulating AMP-PC interactions. 3. Identify molecular signals regulating the function of PCs and AMPs. PUBLIC HEALTH RELEVANCE: We have recently identified a novel niche that regulates specification of stem cells in the Drosophila intestine during organogenesis. The Drosophila midgut bears many striking similarities to that seen in the human intestine. Therefore the results of our research should provide valuable insights into the pathogenesis of human disorders such as cancer and organ dysplasia.